For recent years, a roofing material made of a resin film having an excellent daylighting property, light weight etc. has been more frequently laid on the roof of an athletic facility for soccer football, rugby football, American football, swimming or other sports, or on the roof of a place where a move is shown or a concert is held. As part of noise countermeasures around such facilities, the roofing material is required to be provided with a sound insulating property and a sound absorbing property. From this point of view, an investigation has been made to lay a film on an inner side of a roofing material through an air layer to serve as a sound absorbing film to prevent a sound from leaking outside the facility. When such measures are taken to prevent a sound from leaking outside the facility, the film is required to have a sound absorbing property of absorbing a sound because it is important to simultaneously prevent reverberation from being generated due to sound booming in a facility.
For example, Patent Document 1 discloses a technique that a film with fine through holes formed therein serves as a sound absorbing film, and recites that the through holes are formed as tapered through holes in the film such that the through holes have different opening diameters on a front side and a rear side of the film to improve a sound absorbing property.